Firebase provides a Transit Open Data Set which contains the realtime locations of public transit vehicles in several major US cities, including San Francisco MUNI. The data set also contains GeoFire data for each vehicle which we used to create this demo. Drag around the purple circle to the left to see the vehicles which are currently within its radius. The results update in realtime as you move the circle and as vehicles travel around the city. GeoFire handles all of the hard work, telling you exactly when vehicles enter and exit the circle. It also selectively loads only the data geographically close to the circle, meaning GeoFire data for buses in New York or Chicago are not loaded into memory unnecessarily.
GeoFire is ready for your production apps and plays nicely with the full suite of products offered by Firebase. Read our blog post on GeoFire to get started and then head over to GitHub to read the full API reference, view example code, and find download instructions for all of the GeoFire clients.